FreakyFast

Hey all. I just bought a used Trek 3700 and put a new rear derailluer on there (well, the LBS put it on, after I spent about a day failing). The front has 3 chainrings, but no derailluer. I want to go down to just one chain ring in the front (I believe it is 48 tooth), with an 8 speed cassette in the back.

What, if anything, would I need to worry about when doing this? It seems like that set up would create stress on the chain.. but maybe it would be fine. Could I put a front derailleur on there, simply to help guide the chain straight onto the front chain ring? I'm trying to tackle very small mechanical projects, cause larger ones have always left me frustrated and sulking up to the bike shop.

FBinNY 

If there's no front derailleur you could simply place the chain on the preferred chainring, and it'll stay there until you move it. If you have a FD, you could mount it and use the limit screws to lock it in place, say over the middle chainring and it'll help keep the chain in place.

There' no need to remove the inner ring since it's not doing any harm down there, but if you choose to, be aware that the crank has to be removed first. If you're using only the middle ring, you have a choice about the outer. You can remove it, but you'll need either 5 spacers to make up it's thickness, or replace the chainring bolts with shorter ones made for single chainrings.

What I've done in the past is to file off all the teeth on the outer ring (hold coarse file steady and spin the crank) and left the rest of tin place as a chain or bash guard.

FreakyFast

Thx. Are there any issues regarding chain length, if I switch to a larger chain ring in the front... I imagine not, becuase derailleurs are designed to adapt to three different chainring sizes in the front... but I just want to make sure... I've had wierd issues before due to improper chain length (according to LBS guy this is why my bike wasn't working before)

dsbrantjr

If you switch to a larger chain ring you will absolutely need a longer chain. If it is not long enough you risk doing serious damage to your bike. Here's an article which descsribes the process for determining the correct length: https://sheldonbrown.com/derailer-adjustment.html#chain

FreakyFast

thanks. Yeah, I've heard that too tight a chain can cause issues. I wonder if that's why my old Raleigh frame literally broke in half... the chain was really tight on there. Thanks.